This invention relates in general to cushions for seating and more particularly to a modular wheelchair cushion which has a shaped foam base, a fluid filled or foam cellular pad covering the rear part of the base, and a fabric cover enclosing the base and the pad.
Those who must spend extended time in wheelchairs run the risk of tissue breakdown and the development of pressure sores, which are extremely dangerous and difficult to cure. These pressure sores are decubitus ulcers, typically formed in areas where bony prominences exist, such as the ischia, heels, elbows, ears and shoulders. Typically, when sitting much of the individual's weight concentrates in the regions of the ischia, that is at the bony prominences of the buttocks and unless frequent movement occurs, the flow of blood to the skin tissue in these regions decreases to the point that the tissue breaks down. This problem is well known and many forms of cushions are especially designed for wheelchairs for reducing the concentration of weight in the region of the ischia, and these cushions generally seek to distribute the user's weight more uniformly over a larger area of the buttocks.
Another area where problems occur is in the trochanter area and both cushions and bases for the cushions are shaped so that the thighs are loaded and pressure is relieved on the ischia and the trochanters. Still another problem with wheelchair type cushions is stabilization of the user so that he has a feeling of security when sitting in the wheelchair.
I have a number of patents showing cellular cushions which comprise an array of closely spaced air cells which project upwardly from a common base and are interconnected. These cushions combine the most uniform distribution of weight and thus provide the greatest protection from the occurrence of pressure sores. Since the air cells communicate with each other, all exist at the same internal pressure and each air cell exerts essentially the same restoring force against the buttocks, irrespective of the extent to which it is deflected. U.S. Pat. No. 4,541,136 shows a cellular cushion currently manufactured and sold by Roho, Inc. of Belleville, Ill. for use on wheelchairs.
The stability problem has been attacked by the use of shaped bases, such as shown in Graebe U.S. Pat. Nos. 4,953,913, 5,317,773 and U.S. Pat. No. Des. 342,411 and Jay U.S. Pat. No. 4,726,624. These bases are generally used in injunction with cushions and Graebe U.S. Pat. No. 4,953,913 has been used in conjunction with a cellular cushion and a fabric cover. The stability problem also has been addressed in the cellular cushion field by the use of zoned areas of inflation as shown in Graebe U.S. Pat. No. 4,698,864 which shows a zoned cellular cushion with cells of varying height and Graebe U.S. Pat. No. 5,052,068 which shows another form of zoned cushions with cells of different heights.
Graebe U.S. Pat. No. 5,111,544 shows a cover for a zoned cellular cushion which keeps the cells from deflecting outwardly. This cover has a stretchable top, a skid resistant base and a non-stretchable fabric side panel area.
Patents which use a shaped base, i.e., my U.S. Pat. Nos. 4,963,913 and 5,317,773 and Jay U.S. Pat. No. 4,726,624 use a raised center pommel on the front of the base to direct the location of the legs of the user. However, the raised pommel can be uncomfortable and interferes with the ability of the user, particularly male users, to effect a slide transfer off the front of the cushion when exiting the wheelchair. The pommel also interferes with the ability of the user of the chair to sit on the front edge of the chair, e.g., while eating at a table or working at a desk.
Another problem with a raised fixed pommel is that the location and direction of the legs is fixed and cannot be adjusted to the needs of the user.
Accordingly one aspect of this invention is directed to a solution to the problem of a raised fixed center pommel on a relatively rigid base.
Another problem with foamed bases is the matter of balancing durability, weight, strength, softness, strength or rigidity, and porosity. It is desirable to have a strong durable base which is both light in weight, has a soft feel in desired areas, and still has a relatively fluid impervious surface so that it does not absorb urine or other body fluids and can be readily cleaned. This problem is of more with waterblown foam bases than it is with hydrofluoride blown foams.
Thus, another aspect of this invention is directed to a solution to the problem of providing a fluid impervious, readily cleanable skin on a shaped foamed polyurethane foam base to provide a composite which has the required durability, strength and soft feel.
The present invention resides in a foamed base having a flat rear area onto which may be fastened a variety of resilient pads, including those which have a shaped surface to conform to body shapes, preferably a pad formed with upstanding air inflatable cells. Preferably, the base has a slightly raised front section which has a flat center pommel area. The entire raised front section has a relatively flat top surface except for two angularly inclined slight depressions to accommodate the legs of the user. The transition between the flat rear area and the raised front area is a smooth gradual shape which provides a soft transition between the two areas. This base is designed so as to facilitate slide transfer of the user to and from the base. A removable pommel is provided and is attachable and detachable to the flat center area of the front section of the base to assist in positioning and locating the legs of the user with respect to the cushion. A fabric cover forms the outside of the composite cushion and has a portion of the top formed of stretchable material and the remainder of the top and sides formed of a slick non-stretchable fabric with a skid resistant base. The base by itself is useful by able bodied persons who have good tissue bulk around their legs, whereas disabled persons who do not have good thigh bulk benefit by having a fluid filled module, such as an inflated air module, or a suitable foam module installed on the rear area.
Another facet of this invention is a foam base having a soft blown foam body which is liquid permeable and a separate skin member adhered to the top surface thereof during the blowing process, with the skin being liquid impervious, durable and stretchable at room temperature. With the softer; less dense foam of this application (necessitated by the use of water based blowing agents), the foam cannot be made self-skinning as is the case with hydrofluoride gas blown polyurethane without making the bases more dense and thus undesirably heavy.
This invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.